Chipotle says it stopped serving pork at hundreds of its restaurants after suspending a supplier that violated its standards.

Chris Arnold, a spokesman for the burrito chain, told The Associated Press it's the first time the company stopped serving a topping for its burritos and bowls.

He said Chipotle learned of the violation by the supplier on Friday through a routine audit, and did not have a timeline for when carnitas would return to affected stores, about a third of its total base.

'It's hard to say how long it will last,' he said.

Removed: Chipotle said a third of its stores are no longer serving the carnitas filling because of concerns over how pigs were being treated

In New York City on Tuesday, a sign on the door of a Chipotle location stated: 'SORRY, NO CARNITAS.'

Arnold said most of the issues related to the violations concerned the housing for the pigs. Chipotle demands that its suppliers raise pigs in humane conditions with access to the outdoors, rather than in cramped pens.

On other occasions, Chipotle customers may have noticed signs saying a restaurant is serving meat that doesn't meet the company's 'responsibly raised' standards. That's typically because Chipotle has trouble securing supplies of beef raised without antibiotics or hormones, Arnold said. The company then serves beef that was 'conventionally raised.'